The present invention relates in general to devices and techniques for manipulating the individual pieces of a stack of pieces, and in particular to a new and useful device for separating or unpiling a stack, by layers, particularly a stack of lumber or timber pieces.
In a prior art device of this kind, a stacked layer in its full length, is shifted off the remainder of the stack. The layer is then deposited on a receiving structure provided behind the stack, where the stack layer is taken apart. Such a device requires at least double the length of the stack, and thus a considerable amount of space. In addition, an operation of shifting a complete stack layer out of the stack is very time consuming.
A device for automatically supplying working machines with long pieces that are withdrawn from an orderly arranged stack, is known from German AS No. 2,323,227. With this device a stack layer is pushed transversely off a stack, by means of engaging members and then taken apart by shifting the individual pieces in their longitudinal direction. A transverse pushing, however, is possible only if the sliding surfaces of the layers in the stack, are absolutely smooth. Such a device also requires that all the individual pieces of a stack layer have exactly equal thicknesses and are absolutely even, that is, not warped, bent, or the like. Otherwise the device requires the use of a plurality of regularly spacer elements or so called stickers, provided transversely between every two stack layers. Since such ideal conditions rarely occur, in practice, a transverse shifting of a stack layer is possible only when a stack with stickers is used.